Pneumatically operated chute door

ABSTRACT

A chute system having a pneumatically actuated access door where the door is journally mounted to an access port in the wall and communicates with the chute to direct objects inserted into the access port to the chute. When an operator actuates a switch, the door may be opened by a pneumatic forcer connected between the access port frame and the door so as to form a lever arm about the door journal. The pneumatic forcer is mounted to the door with a slidable journal such that the door may be opened manually. The duration of the open state of the door is determined by a timing mechanism which removes the pneumatic pressure after a time has elapsed, enabling a spring to urge the door into the closed position.

This application claims the benefit of U.S. provisional application No.60/536,798, filed on Jan. 15, 2004, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

This invention relates to the art of chute systems, and moreparticularly to chutes for the collection and disposal of refuse ofvarious kinds, as well as the collection and distribution of materials.Further, this invention relates to a mechanism for opening a chute door.

Chute systems are found in numerous applications, such as for thecollection of trash in high rise buildings, the collection of laundry inhotels and hospitals and for the collection of medical or other waste.They may also be found in materials handling applications in industrialfacilities. For safety or sanitary reasons, chute systems may be fittedwith a door closing the opening into the chute during times thatmaterial is not being introduced into the chute. This prevents thedischarge of particulate matter, odors or other contaminants into thesurrounding environment. Also, in the case of a fire or explosion in thechute system, the door provides a barrier which mitigates the effect ofthe event.

Existing door systems are normally manually operated where the operatoropens the door, inserts the material for which the chute is designed,and closes the door. Doors may be fitted with an opening handle and alatch mechanism, such as may be found on a conventional room door, toensure that the door remains closed when not in use, and may also befitted with a closing mechanism to urge the door closed. The closingmechanism may be in the form of a spring, with coil spring, leaf springair spring and pneumatic spring mechanisms being known in the art.

Manually operated doors normally require that the operator use one handto open the door, and to hold the door open during the period where thematerial is being introduced into the chute system through the door. Ifthe load is heavy or the operator is handicapped, this may be bothawkward and dangerous. In addition, a manually operated door may beopened even if dangerous conditions exist in the chute system, such as afire, smoke or noxious fumes.

Electrically operated chute doors are known, and they mitigate some ofthe problems mentioned above, but themselves have disadvantages. Complexmechanical linkage mechanisms are required to effect the door openingand closing, and the electric motor is susceptible to overheating andburn out in the event the door becomes jammed in any position, open,partially open or closed. One means of preventing the continuedoperation of the motor is to place the motor on a timer, but the motorwill operate against the resistance of the jammed door for the entireperiod that the timer permits. Other means of preventing the continuingoperation of the motor include microswitches to sense the open andclosed position of the door. It is well known that microswitches presenta maintenance and adjustment problem. Another problem associated knownelectrically actuated doors is that the mechanical linkage mechanism maynot permit the door to be opened manually. Attempting to open the doormanually may place undesirable stresses on the mechanical linkages andresult in a requirement for frequent maintenance.

BRIEF SUMMARY OF THE INVENTION

Features of the present invention may mitigate the difficultiespreviously described, as well as improve the operation and safety ofchute systems. These objectives are achieved while minimizing thecomplexity of the mechanical components needed to effect the automaticopening and closing of the chute door.

In accordance with the present invention, a chute system, which is agenerally vertically oriented enclosed space, having a vertical extentgenerally at least equal to the highest story of a building or facilityto be serviced, is fitted with a door assembly at each story to beserviced by the system. The chute itself is normally enclosed in afireproof material for safety reasons. The door assemblies areconstructed of material ordinarily intended to retard fire or explosionin accordance with local or industry building codes, or to meet therequirements of the designer. The opening of the door is initiated by anoperator actuating a switch located in proximity to the door, or by asensor that determines the presence of an operator. The door may bedisposed such that it is journalled to a frame which is mounted so as tofill an opening in the wall of the chute system, the door closing anopening in the frame when the door is in a closed position. In oneaspect, the door may be mounted such that, when it opens, an end of thedoor distal to a journalled base end rotates outwardly (that is, towardsthe operator) with respect to the chute such that the door makes anangle of approximately 45 degrees with respect to the horizontal whenfully opened, although other orientations and opening limits may beemployed. The extent and direction of the door opening and depends onthe specific design requirements. Preferably the angle is less than 90degrees with respect to the horizontal, so as to provide an inclinedsurface to direct the material into the chute.

A pneumatic supply, which may be installed in a common area, providespressurized air to one or to a plurality of door opening mechanisms.When the opening of a door is initiated as described above, pressurizedair is introduced into a main pneumatic cylinder or pneumatic forcerdisposed between the door and the door frame of the door assembly. Themain pneumatic cylinder rod actuates in response to the air pressure andurges the door open. The door is rotatably moved from a closed positionto the fully opened position. A spring is also connected between theframe and the door, and it is actuated by the opening and rotation ofthe door, resulting in the development of a restoring force about thejournal, said force initially being less than the opening force exertedby the main pneumatic cylinder. The door continues to rotate until amechanical limit is reached, or the rotational forces about the journalexerted by the main pneumatic cylinder and the spring balance eachother.

The door is held in its open position as long as the pneumatic pressureis applied to the main pneumatic cylinder. The time duration of thispressure is controlled by a pneumatic timer valve. The duration may befixed or adjustable in accordance with the details of the design. At theend of the opening time period, the pneumatic pressure is relieved inthe main pneumatic cylinder and the pneumatic spring urges the doorclosed. Mechanical or pneumatic springs may be used.

In accordance with another aspect of the present invention, the door isalso capable of being opened manually. The main pneumatic cylinder isattached to the door and to the frame such that a force applied to theoutside of the door by an operator grasping a provided handle isoperable to rotate the door as if it had been urged by the mainpneumatic cylinder. The door may be opened to any rotational extentbetween the closed position and the fully open position. A restoringforce is provided by the spring so that the door will close when theoperator releases the handle. In this manner, the door may be openedmanually if the operator desires, and the door may be opened even incase of a fault in the pneumatic system.

In accordance with still another aspect of the present invention, thedoor may have a latch mechanism to secure the door in a closed position.This may be similar to a conventional door latch where a bolt in thedoor is urged by a spring so as to engage an opposing hole in the frame,or some similar arrangement. In order for the pneumatic openingmechanism to operate to open the door, this bolt must be released at thebeginning of the opening operation. An actuator may be arranged in thehole in the frame engaged by the bolt so as to urge the bolt towards thedoor such that it no longer engages the hole in frame. The actuator mayoperate by electrical or pneumatic means, and may have a spring returnsuch that it retracts when the activating means is discontinued,permitting the latch to re-engage the hole in the frame as the doorreaches a closed position. Alternatively, the actuator may be urged intoa retracted position by the spring force applied to the latch bolt whenit is positioned opposing the hole in the door frame.

In any aspect of this invention, the pneumatic operation of the door maybe prevented if there is an unsafe condition in the chute as determinedby one or more temperature sensors or one or more smoke or contaminantsensors. In particular, a sensor may be installed in a collection areaat the base of the chute to determine if a sensing threshold has beenexceeded and to actuate a shut off valve to interrupt the pneumaticsupply to the door actuation mechanism. Preferably, the pneumaticpressure being supplied to the door assemblies may also vented to theambient environment when the solenoid is actuated so that a door cannotbe pneumatically opened with any residual air pressure in the system.This feature prevents the door from opening or remaining open for apreset time due to residual pressure in the pneumatic supply when thereis a safety hazard determined by the appropriate sensor. In addition, alocking mechanism may be provided for each door, which operates toprevent opening of the door where an unsafe condition has beendetermined to exist by a sensor. A locking mechanism may also act toprevent the opening of the door when another door in the chute system isopen.

The pneumatic supply may be located inside or outside of the chute, andthe pneumatic pressure supplied to a plurality of doors by a flexiblehose, which may be enclosed in a conduit for mechanical protection.

The door may be fitted with flanges, mounted near the two verticaledges, and extending towards the chute so as to guide the material intothe chute. The height of the flanges may vary from a high value at thebase of the door where the door is journalled to the frame, to a lowvalue at distal end of the door. The lower ends of the rods extendingfrom the main pneumatic cylinder and the pneumatic spring that are moredistal from the cylinders of each may be journally attached to flangesnear the base of the door. The flanges are preferably mountedorthogonally to the door and facing the chute, and may be positionednear the side edges of the door. The rods are journally attached to thedoor flanges at the flange end closest to the door journal, positionedsuch that a suitable lever arm exists between each attachment point atthe flange end closest to the door journal and the door journal. Theends of the cylinders more distal from the rods are each journallyattached to the frame, to a flange extending from the frame, or to afairing joining the frame to the chute.

Alternatively, a strut may be disposed near the base end of the door,extending orthogonal to the door surface, in the direction of theinterior of the chute. The distal end of the rod extending from the mainpneumatic cylinder may be connected to the strut so as to create a leverarm with respect to the door journal. The spring may also be connectedin this manner. Further, the strut may be connected directly to thejournal, or an extension thereof.

The rod of the main pneumatic cylinder may be restrained by a slidingbracket, which may be journalled to the door flange or the strut suchthat the door may be opened manually as an alternative means ofoperation, or in the event of failure of the pneumatic supply.

The main pneumatic cylinder and the spring may be positioned such thatthey are disposed between the door flanges and the door frame, orbetween a strut and the door frame, such that the width of the door isnot increased over that of a manually operated door, while providing thesame width of opening. Alternatively the main pneumatic cylinder and thespring may be attached to a strut extending orthogonal to an extensionof the door journal, such that the strut is not positioned within thedoor opening in the frame

In addition, the actuating switch for initiating the opening of the doormay be located on the door frame or at some other convenient location.The pneumatic control mechanism may also be located on the door frame orat some other convenient location.

These and other advantages of the present invention will become apparentto those skilled in the art on reading the following detaileddescription and viewing the drawings, in conjunction with the claims.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a elevation cross-section view of a chute system in accordancewith an aspect of the present invention having a plurality ofpneumatically actuated access doors;

FIG. 2 is a front view of a pneumatically actuated access door inaccordance with an aspect of the present invention showing an operationswitch and a handle for manual operation;

FIG. 3 is a rear view of the pneumatically operated door illustratingthe placement of the main pneumatic cylinder and the air spring in anembodiment of the present invention;

FIG. 4 is a side view of the pneumatically operated access door ashowing aspects of the door in a closed and an open position;

FIG. 4A is a detail taken along line A-A of FIG. 4, illustrating theoperation of the latch bolt in accordance with an embodiment of thepresent invention;

FIG. 4B is a detail illustrating the relationship of the journalledslide bracket to the rod of the main pneumatic cylinder when the door isin a closed position, and when the door has been manually orpneumatically opened;

FIG. 5 is a block layout diagram illustrating the control system for thepneumatically actuated door;

FIG. 5A is a detail of the pneumatic supply for the situationillustrating a connection of the interlock latch to the pneumatic supplyFIG. 6 is a detail of the pneumatic supply for the situation where thedoor may be locked closed when another door has been opened.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be better appreciated with reference to thedrawings and description, which are understood as representing aspectsof the invention, but not intending to limit the scope thereof, which isset forth in the claims. Corresponding elements in drawings areidentified by the same numeral or symbol.

FIG. 1 illustrates a chute system including the pneumatically actuateddoors. The chute system 1 comprises a vertical enclosure 2 designed tomeet mechanical, environmental and safety requirements associated withthe structure in which the chute system 1 is to be installed. Inside thevertical enclosure 2 is a chute 3 extending from the lower end of thevertical enclosure 2 to the top end of the vertical enclosure 2, withthe base end 4 of the chute 3 being closed by a flap 5 held in place bya spring (not shown) or a counterweight (not shown) such that thematerial introduced to the chute 3 can open the flap by the weight ofthe material and be deposited in an area 7, which is typically a trashroom or service area, for subsequent removal. The upper end of thevertical structure 2 may extend through the roof and be fitted with aventilation cap 8 such that odors may be exhausted to the outside air,and to provide access to the chute system for maintenance.

Each floor requiring access to the chute system is provided with apneumatically actuated access door 6, whose operation will be describedlater. The motive power to operate the pneumatically actuated accessdoors 6 may be provided by an air compressor 8 and an air distributionsystem 9. The air distribution system has a shut-off valve 10 formaintenance purposes and a solenoid shut-off valve 11, whose operationis controlled by a sensors 12, which may be temperature, smoke or otherenvironmental sensors such that, if a preset threshold is exceeded, theair supply is not provided to the pneumatically actuated access doors 6.The air from the compressor 8 is supplied to each of the pneumaticallyactuated access doors 6 by a flexible tube. The tube may be made of ¼″HD polyethelene tubing or similar material and the tube may be containedin a flexible conduit 13 to protect the tube against damage from thematerial being introduced to the chute 3. In the event that the solenoidshut off valve 11 is actuated, the flexible tube may be vented to theambient environment such that residual air pressure is removed from thepneumatically actuated access doors 6.

As will be described later, the air supply is routed to each floor insequence by a method that permits the independent actuation of any of aplurality of pneumatically actuated access doors 6. More than one doormay be independently actuated to open during a particular time periodor, alternatively, the pneumatic control system may permit only one doorto be open at a time. Depending on the number of floors in theinstallation, it may also be desirable to deliver the air in a largertube to a higher starting floor, thus segmenting the system into zones,and ensuring adequate air pressure throughout. A separate compressor 8may be used for each zone, or multiple compressors used for redundancy.

The chute 3 may be square, rectangular, circular or any other regularcross section, depending on the design requirements. The pneumaticallyoperated door assembly 6 penetrates the vertical structure 2 through anopening 14 provided in the vertical structure 2, and also in anyconventional structural walls enclosing the chute system. Additionallyit penetrates the chute 3 such that a fairing 44 may join the frame 21(see FIG. 4) of the pneumatically actuated access door assembly 6 andthe chute 3 so as to prevent material from entering the space betweenthe vertical structure 2 and the chute 3.

The chute 3 may be constructed of prefabricated components having anappropriate cross section, and being stacked one on top of another, withattachment members to keep the sections in alignment. Preferably asupport 17 is provided for the chute by connection to the verticalstructure 2.

FIG. 2 is a front view of a pneumatically actuated access door assembly6 in a closed position. The door 20 is fitted to a frame 21 which issized to fit the hole 14 provided in the vertical structure 2,corresponding to the opening in the chute 3. The frame 21 may bemanufactured of welded steel elements such as angle brackets, bent sheetstock and the like. Materials other than steel which meet the safety anddesign requirements may be used. At the upper end of the frame 21 acover plate 22 provides access to the pneumatic door control unit 51,and may support the door opening command switch button 23. Pressing thecommand switch button 23 initiates the door opening process, which willbe described later. FIG. 3 is a partial back view of the pneumaticallyactuated access door assembly 6. The main pneumatic cylinder 31 orpneumatic forcer is disposed such that the upper end is journalled tothe rear of the frame 21 or to a flange 44 extending rearward from theframe 21, adjacent to the door 20, and the lower end, being anextensible rod 25 extending from the main pneumatic cylinder 31, passesthrough a journalled slide bracket 30 attached to a door flange 26 whichmay be orthogonal to the door 20 and which projects towards the chute 3.A door closing device, which may be an air spring 32, or a metal springor the like may be journalled to the rear of the frame 21 or to theframe flange 44 at a side opposite that of the main pneumatic cylinder31, at its upper end and journally connected to a door flange 26.Alternatively, both the door closing device and the main pneumaticcylinder may be located at the same side of the door.

FIG. 4 shows a partial side view of the pneumatically actuated accessdoor assembly 6, illustrating the door 20 in both an open and closedaspect. When the door is in a closed position, the rod 25 of the mainpneumatic cylinder 31 is in an extended position, and the rod 34 of theair spring 32 is in an extended position, when measured with respect tothe positions of each respectively, when the door is in an openposition. Operation of the journalled slide 30 will be describedsubsequently.

FIG. 5 is a layout of an embodiment of the pneumatic door control unit51. This may be located behind the access panel 23 at each pneumaticallycontrolled access door assembly 6. Alternatively, the pneumatic doorcontrol unit may be located at some other convenient place and only thepneumatic pressure needed to actuate the door supplied to the doorassembly 6. The air supply from the compressor 8 may be routed in turnto each of the pneumatic door control units 51 by the conduit enclosedflexible hose 13. The pneumatic door control unit 51 consists of a timer52, an compressed air routing switch 53, a bolt actuation mechanism 54,if required, the operator command switch 55 and air distribution andregulation components, which will now be described in conjunction withthe operation of the pneumatic door control unit 51.

The air supply 13 a enters the pneumatic door control unit 51 through anentry box, and is fed to a “Y” connector 56, connected such that one ofthe legs of the “Y” connector is connected to another conduit enclosedflexible hose 13 b that exits the pneumatic door control unit 51 andcontinues to another pneumatically controlled access door assembly 6.The remaining leg of the “Y” provides the compressed air supply to thepneumatic door control unit 51. The air supply is routed to a “T”connector 58. An output of the “T” connector 58 is routed to an inputport 59 of the operator command switch 55, which may be a push-buttonswitch, lever switch or similar air control device or it may be a devicethat senses the presence of a person, such as an infra-red detector.Ordinarily this switch will be of a momentary-operation type and permitthe air to flow from the input port 59 to the output port 60 when it isactuated by depressing the operator command button 23. The output 60 ofthe operator command 55 switch is routed to the input of a two portalternate action transfer valve 53. The input to the two-port alternateaction transfer valve is the other output of the “T” connector 58, andthe output port 62 of the two-port alternate action transfer valve isfed to the input port 65 of the pneumatic timer valve 52 through a “T”connector 63 and a splitter 64.

The pneumatic timer valve 52 may have a manual adjustment means, such asa knob 71, which is arranged such that it controls the time duration ofthe cycle.

When the operator command button 23 is depressed, compressed air presentat the input port 59 of the operator command switch 55 is permitted toreach the output port 60 while the operator command button 23 continuesto be depressed and is then routed to a first control port 66 of thetwo-port alternate action transfer valve 53, causing the valve to switchsuch that the compressed air routed to input port 61 thereof is allowedto reach the output port 62. Once this switch action occurs, thetransfer valve remains in this state, even if the operator commandbutton 23 is released, until there is a pneumatic input to the secondcontrol port 67. The compressed air output 62 from the transfer switchis routed through a “T” connector 63 to actuate the main pneumaticcylinder 31, to apply air pressure to the pneumatic timer valve 52, andto also supply air pressure to the latch release mechanism 54, ifrequired. A flow control regulator 68 is inserted in the output of the“T” connector between “T” connector 69 and the input to the mainpneumatic cylinder 31. The flow control regulator 68 functions toregulate the rate at which air can be supplied to the main pneumaticcylinder 31. The flow control regulator 68 provides for an adjustment toregulate the rate at which the door 20 opens when the air pressure isapplied, and may also be used to compensate for pressure drops in thefeed lines, which may depend on the distance between the compressor 8and a specific door 6.

An output of the “T” connector 64 is routed to the pneumatic timer valve52. When air pressure is applied, the timer valve 52 begins the timingcycle in accordance with a preset value. When the time has expired, thecompressed air is routed from the input port 65 of the timer valve 52 tothe output port 70 of the timer valve 52. The compressed air output fromthe timer valve 52 is routed to the input of the second control port 67of the two-position transfer valve 53, causing the switch to return toits original position, thus removing the air pressure from the mainpneumatic cylinder 31, the timer 52 and the latch release 54 (ifinstalled).

With the operation of the pneumatic control unit having been described,the physical operation of the door is now described. As shown in FIG. 4,the door 20 is journalled 43 at its base end to the frame 21, and boththe main pneumatic cylinder 31 and the air spring 32 (not shown in thisview) are connected between an upper side of the door frame 21 or doorflange 44 and an end of the door flange 26 proximal to the journal 43.The locations of the journal attachment points on the door flange 26 arespaced such that a lever arm is created between each attachment pointand the journal 43. When the operator command button 55 is actuated, thepneumatic control unit acts to apply compressed air to the mainpneumatic cylinder 31. This urges the push rod 25 to retract into thecylinder 31. The stop 27 (FIG. 4B) comes into contact with the lower end29 of the journalled slide bracket 30 and applies and a rotational forceabout the journal 43 that attaches the door 20 to the frame 21 urgingthe door 20 to rotate about the journal 43 so as to open. As the door 20begins to rotate open, the rod 34 of the air spring 32 is urged into theair spring 32 and the restoring force increases as the rod 34 is urgedfurther into the air spring 32. This results in rotational force appliedthrough a lever arm on the journal 43 resisting the opening forceprovided by the main pneumatic cylinder 31.

The door rotates about the journalled axis 43 so as to swing from thevertical towards the horizontal, but its motion is stopped at a pointwhich may be determined by one of several design methods. The mainpneumatic cylinder rod 25 may reach the full extent of its permittedmotion into the cylinder 31, a mechanical stop may be constructed suchthat an extension of the door 20 abuts the frame 21 after a specificangular rotation, or the restoring torque developed by the air spring 32becomes equal to the opening torque provided by the main pneumaticcylinder 31, when measured about the journal 43.

Once the door has rotated to its open position 20 a, and motion has beenstopped, by any of the previously described mechanisms, the operator mayintroduce the desired material into the chute. The door remains open,since the pneumatic pressure continues to be applied to the mainpneumatic cylinder 31. After the expiry of the preset time interval, thetimer 52 permits the application of air pressure to the second controlport 67 of the two-port transfer switch 53 such that the compressed airis no longer supplied to the main pneumatic cylinder 31. At this timethe opening force is reduced as the air pressure is vented outside thecompressed air system through a breather 72 fitted to the two-portcontrol valve 53, the rod 34 extends and the air spring 32 urges thedoor 20 to return to a closed position. The door 20 rotates to theclosed position, and the latch reengages.

The operation of the main pneumatic cylinder 31, the air spring 32 andthe journalled slide bracket 30 are now further described in the contextof an opening and closing sequence of the door 20 by pneumatic means.When the door is in a closed position, the rod 25 of the main pneumaticcylinder 35 is in an extended position and the rod 34 of the air spring32 is in an extended position. The air spring 32 may continue to exert asmall force urging the door 20 closed against the frame 21. This mayhelp ensure proper closure of the door over a period of use when thefriction in the journal 43 may increase, or due to misalignment ofmechanical components. When the door open command button 23 is pushedand air pressure is applied to the main pneumatic cylinder 31, the airpressure urges the rod 25 to retract into the main pneumatic cylinder31. The stop 27 comes into contact with the bottom end 29 of the slidebracket 30, resisting the retraction of the rod 25, and urging the door20 to rotate about the journal 43. As the door 20 begins to rotate to anopen position 20 a, the rod 34 of the air spring 32 is urged into theair spring 32 causing the air spring 32 to increase the resistance tofurther entry of the rod 34. This increased force may be used to limitthe motion of the door 20 to a maximum rotation, or a mechanical stopmay be used. When the door has reached its maximum rotation it isrestrained from closing by the continued force exerted by the mainpneumatic cylinder 31 until such time as the pneumatic control unit 51removes the air pressure from the main pneumatic cylinder 31 and permitsthe pressure to vent to the external environment through the breather70. As the removal of air pressure results in a greater rotational forcebeing applied by the air spring 32 than is being applied by the mainpneumatic cylinder 31, the door 20 is urged to rotate into a closedposition. As the door 20 rotates into a closed position, the rod 25extends from the main pneumatic cylinder 31, being urged to do so by theforce exerted by the bottom of the slide bracket 29 on the stop 27.Since the air flow out of the main pneumatic cylinder 31 may berestricted, some opposing force to closure may be encountered, with themain pneumatic cylinder 31 acting as a damper during this portion of thecycle. During the closure of the door, the rod 34 extends from the airspring 32 in response to the urging by the force built up in the airspring 32 during the opening part of the cycle.

If the door begins to close before the operator has completedintroducing the intended material, the operator command switch 23 mayagain be actuated, the air pressure reapplied and the timer reset as ifa new door opening cycle had been commenced. Since the air pressure willbe limited to that of the air supply to the pneumatic control unit,reapplication of the air pressure prior to door closure does not causeany damage or malfunction.

The means of attachment of the lower end of the main pneumatic cylinderrod 25 to the door flange 25 by the journalled slide bracket 30 is suchthat the door may be opened manually from outside the chute by pullingon a handle 24 attached to the door 20, after rotating the handle, orotherwise disengaging the latch bolt 74. The journalled slide bracketassembly 30, being slidably attached to the rod 25 and journalled to thedoor flange 26, may slide with respect to the rod 25 such that the rod25 may remain in its extended position with respect to the mainpneumatic cylinder 31 when the door is being opened manually. To do thisthe slide bracket assembly 30 slides along the push rod in the directionopposite to the stop 27, and thus does not exert any force on thejournal 43. The opening of the door 20 in the manual mode is resisted bythe entry of the rod 34 into the air spring 32. The door may be manuallyopened until either a mechanical stop prevents further rotation, or theoperator has exerted a force equal to that of the restoring force of theair spring 32, as determined about the door journal 43, or the airspring has reached its maximum travel in the compressed direction. Whenthe door is manually operated and reaches an open position, and theoperator releases the handle 24, the restoring force of the air spring32 urges the door closed.

FIG. 4B illustrates the relationship of the journalled slide bracket 30to the rod 25 in several aspects of the door position. When the door 20is in a closed position, the rod 25 extends through the journalled slidebracket such that one end enters the main pneumatic cylinder 31, and theend more distal from the cylinder is terminated in a stop 27. The stop27 may be threaded and inserted into an end of the rod 25 such that thedistance between the stop 27 and a lower surface 29 of the journalledslide bracket 30 may be adjusted for the situation when the door is in aclosed position. Alternatively, the end of the rod may be threaded andone or more nuts threaded onto the rod to achieve a similar adjustment.The stop 27 may also be applied to the end of the rod 30 by swaging,welding or other technique that may not permit adjustment.

The journalled slide bracket 30 may be journally attached to the doorflange 26 by a pin or bolt 28 so that the rod and the door flange 26 mayrotate angularly with respect to each other when the door 20 is openedby rotation about the journal 43.

When air pressure is applied to the main pneumatic cylinder 31, the rod25 is urged into the main pneumatic cylinder 31 and, if the stop 27 isnot already in contact with the bottom surface 29 of the journalledslide bracket 30, the movement of the rod 25 into the main pneumaticcylinder 31 causes such contact. As the rod 25 is urged further into themain pneumatic cylinder 31 by the air pressure, the force exerted by thestop 27 on the lower surface 29 of the journalled slide hinge 30 actsthrough the lever arm of the door hinge 26 about the door journal 43providing the rotational force urging the door 20 into an open position.When the door 20 has reached an open position, the relationship of therod, the stop and the journalled slide are shown in FIG. 4B as elements25 a, 27 a, and 30 a, respectively.

When the door 20 is opened manually, the rod 25 is not urged into themain pneumatic cylinder 31 and remains in an extended position, so thatthe stop 27 remains in approximately its original position, but hasrotated angularly as shown in element 27 b. The force to open the door20 is provided by a person operating the handle 24, resulting in arotational moment about the door journal 43. As the door rotates into anopen position, the journalled mounting bracket 30 slides freely alongthe rod 25, permitting the rotation of the door 20 about the doorjournal 43. In this situation, the stop 27 is not in contact with thebottom 29 of the journalled slide bracket 30. When the operator releasesthe handle, the air spring 32 urges the door 20 into a closed positionand the relative positions of the components returns to the aspect shownin FIG. 4B in solid lines.

Another aspect of the present invention is a lockout, shown in FIG. 5A,which prevents the door from being opened manually in the samecircumstances where the door is prevented from being openedpneumatically. A pneumatically operated latch bolt 84 is fitted to theframe 21 such that it engages a hole 85 in the door 20. The latch bolt84 is normally retracted by the air pressure in the system applied topneumatic cylinder 81. When the air pressure is vented to theenvironment, exemplary of a situation where door is to be prevented fromopening, for example, due to an environmental problem, the latch bolt 84engages the hole 85 in the door 20. The latch bolt has a beveled surface87 whose orientation is such that the door may close completely if it isin an open position at the time that the locking event occurs. The doorthen cannot be opened again until the air pressure is restored.

A further aspect of the present invention is a lockout which preventsthe door from being opened whenever another door is open, shown in FIG.6. It also acts in a similar manner with respect to all of the doors inthe event that the main pneumatic supply is vented as described above.The same latch mechanism for preventing the opening the door describedin the previous paragraph may be used, with additional components, whichwill be described. A pneumatic limit switch 62 senses whether the dooris open or closed. When the button 23 of the operator command switch 55of a door assembly 6 is pressed and the door 20 opens as previouslydescribed, the pneumatic limit switch 62 causes the air supply line 63 bto the higher floors to be vented to ambient. The air line 63 b isconnected to the air line 63 a of the next higher floor. The air line 63a is only connected to the main air supply 13 a at the lowest door inthe arrangement (that door being shown in FIG. 6). At the top of theseries of doors having the lockout, the air supply line 63 is connectedto an air supply line 73, which runs from the top door to the bottomdoor, having an input to an “AND” valve at each door. Air pressure isapplied to the pneumatic switch 55 only when air pressure is present inboth the air supply line 63 and the air supply line 73. Thus, if anydoor is open, another door cannot be opened.

The operation of the control mechanism will now be described withparticular reference to FIG. 6, but many alternative arrangements ofrealizing this aspect of the invention will be apparent to personsskilled in the art. In the state where no door is open, air pressure ispresent in air supply lines 63 and 73, and any door may be opened. Inthis state, each “AND” valve 64, having air pressure applied at bothinput ports, is in an “on” state and operates such that air pressure ispresent at an input side of operator command switch 55. When an operatorpresses a command push button 23, the door mechanism operates in anormal manner as previously described. As the door 20 begins to swingopen, this is sensed by the pneumatic limit switch 62, which vents theair supply line 63 b to ambient. Since this supply line is connected tothe air supply line 63 a of the next higher door, the air supply line 63a for the next higher door assembly 6 will not have air pressure, the“AND” valve 64 at the next higher door assembly 6 will be in an “off”state, and no air pressure will be supplied to the input of the operatorcommand switch 55. Thus the next higher door 20 cannot be opened. Thissituation pertains to all higher doors. Although it will be appreciatedthat the process of opening the door initiated in this manner willresult in the “AND” switch 64 for the door being opened changing to the“off” state, as the air supply lines 63 and 73 are vented to ambient bythis action, the pneumatic timer 52 has already been actuated, and theair pressure will be applied to the cylinder 31 for the duration of thedoor opening cycle. This discussion has described the situation where alower door has been opened.

Now the situation where a higher door is opened is described. Since theair supply line 63 is connected to the air supply line 73 at the top ofthe sequence of doors, the opening of any door below the connectionpoint of the two air supply lines will result in the venting of the airpressure in air supply line 73. In this situation, each “AND” valve willbe in the “off” state, and no air pressure will be supplied to any ofthe operator command switches 55, and no other door can be opened.

When the door that is presently open returns to a closed position, theassociated limit switch 62 terminates the venting of air to ambient andresulting in repressurizing the air supply lines 63 and 73 at all of thedoors. Another door may now be opened.

In the situation as described, the lockout cylinder 81 is only suppliedwith air pressure when the door with which it is associated is activatedto be opened. The air pressure applied to the cylinder 81 retracts thebolt 84 from the hole 85 in he door 20, permitting it to be opened. Whenno air pressure is applied to the cylinder 81, a spring 83 urges thebolt 84 into the hole 85, preventing the door 20 from opening.

In a further aspect, the latch release cylinder 54 and the associatedspring loaded bolt 74 may be omitted, and only a pulling handle 24affixed to the door, as the lockout mechanism may serve the purpose ofsecuring the door closed.

In a further aspect, an indicator 65 which senses air pressure may beconnected to the operator command switch side 55 of the “AND” valve 64such that the indicator 65 provides an operator with an indication thatthe door 20 may be opened. Indicators of various types may be used,including those which are directly pneumatically actuated as well aselectromechanical and electronic types.

The invention has been described with respect to a number of exemplaryembodiments. It will be apparent to persons skilled in the art that manymodifications and alterations to these embodiments are practical. Theinvention is therefore limited only by that which is claimed.

1-38. (canceled)
 39. An access door assembly comprising: a surroundingframe capable of being fitted into an opening in a wall; a door beingjournally mounted to the frame such that the door-can swing away fromthe wall; a pneumatic forcer operably connected to the frame and thedoor to rotatably move the door from a closed position to an openposition; and means for supplying pneumatic pressure to the forcer. 40.The access door assembly as in claim 39, wherein the pneumatic forcer isjournally attached to the surrounding frame and is slidably journalledto the door.
 41. The access door assembly as in claim 39, wherein thepneumatic forcer has a pneumatic cylinder and an extensible rod, theextensible rod being slidably restrained and the slidable restraintbeing journalled to the door.
 42. The access door assembly as in claim39, wherein the pneumatic forcer has a pneumatic cylinder and anextensible rod, the extensible rod being slidably restrained and theslidable restraint being journalled to a strut, the strut being mountedso as to form a lever arm with respect to the door journal.
 43. Theaccess door assembly as in claim 39, wherein the pneumatic forcer has apneumatic cylinder and an extensible rod, the extensible rod beingslidably restrained and the slidable restraint being journalled amounting surface, the mounting surface being orthogonal to the door, andarranged such that a rotational force is applied about the door journalwhen the pneumatic forcer is actuated.
 44. The access door assembly asin claim 41, wherein the extensible rod is fitted with a stop at the enddistal from the pneumatic cylinder such that it abuts an end of ajournalled slidable mount as the extensible rod is retracted into thecylinder when pneumatic pressure is supplied.
 45. The access doorassembly as in claim 41, wherein the extensible rod is slides freelywith respect to a journalled slidable mount when the door is manuallyrotated about the door journal.
 46. The access door assembly as in claim39, wherein a spring is operably connected between the surrounding frameand the door, such that the spring generates a restoring rotationalforce about the door journal when the door is moved to the openposition.
 47. The access door assembly as in claim 46, wherein thespring is a coil spring.
 48. The access door assembly as in claim 46wherein the spring is an air spring.
 49. The access door assembly as inclaim 46 wherein the spring is a pneumatic spring.
 50. The access doorassembly as in claim 48 wherein the air spring comprises a pneumaticcylinder and an extensible rod.
 51. The access door assembly as in claim39, having a manually operated securing bolt, the bolt being mounted tothe door such that it opposes a hole provided in the access port frame,wherein the bolt is chamfered at the exposed end and the chamfer facestowards surrounding frame when the door is in an open position.
 52. Theaccess door assembly as in claim 51, wherein a pneumatic cylinder ismounted in the surrounding frame such that it communicates with thebolt, and when the pneumatic cylinder is actuated, the bolt is movedsuch that it no longer engages the hole in the access port frame. 53.The access door assembly as in claim 52, wherein the pneumatic cylinderis actuated during a door opening operation using pneumatic means. 54.The access door assembly in accordance with claim 39, wherein the doorhas a rotatable handle actuating a latch mechanism which must bereleased prior to opening the door.
 55. The access door assembly inaccordance with claim 54, wherein a pneumatic actuator is positioned inthe surrounding frame such that it opposes the latch mechanism, and theactuator extends sufficiently far when actuated so as to release thelatch mechanism.
 56. The access door assembly in accordance with claim55 wherein the pneumatic actuator is actuated whenever the pneumaticforcer is supplied with pneumatic pressure.
 57. The access door assemblyaccording to claim 39, having an interlock bolt in the door, to preventthe opening of more than one door at a time.
 58. The access doorassembly according to claim 57, wherein the interlock bolt is disposedin the surrounding frame, opposing a hole in the periphery of the door.59. The chute system according to claim 58 wherein-the interlock bolt isurged into the hole by a spring, and the interlock bolt is retractedwhen the door is actuated, and no other door is open, the interlock bolthaving a beveled end engaging the hole, the beveled end orientated suchthat the bevel faces outward from the chute, the bolt being extendedwhen the pneumatic pressure is no longer applied to the door, and thedoor acting on the bevel during the closing of the door such that thebolt is depressed sufficiently to permit the door to close, and thebeveled bolt to reengage the hole.
 60. The access door assembly as inclaim 53, wherein the pneumatic cylinder comprises a cylinder and anextensible rod fitted with an end portion distal to the cylinder adaptedto push on the bolt, and said extensible rod being restored to aretracted position by a spring when pneumatic pressure is removed.61.-67. (canceled)
 68. An access door assembly comprising: a framehaving four sides creating an aperture and the frame is adapted to befitted and secured into an opening in a wall; a door mounted to ajournal such that the door fills the aperture when the door is in aclosed position; and a pneumatic forcer operably connected to the frameand to the door to rotatably move the door from the closed position toan open position, wherein the pneumatic forcer is adapted to communicatewith a supply of pneumatic pressure.
 69. The access door assemblyaccording to claim 68, wherein the journal is disposed to adjacent to alower side of the frame, and a door swing direction is towards anoperator of the door.
 70. The access door assembly as in claim 68,wherein a spring is operably connected between the frame and the door,such that the spring generates a restoring rotational force about thejournal when the door is moved to the open position.
 71. An access doorassembly, comprising: means for mounting a door in a wall; a doormounted to the means for mounting a door in a wall using a journal;means for urging the door to an open position.
 72. The access doorassembly according to claim 71, further comprising: means for urging thedoor to a closed position.
 73. The access door assembly according toclaim 72, wherein the means for urging the door to an open positioncommunicates with a pneumatic supply through a pneumatic controlassembly.
 74. The access door assembly according to claim 71, wherein apneumatic control assembly is configured to prevent operation of themeans for urging the door to a open position when another of a pluralityof doors is not in the closed position.
 75. The access door assemblyaccording to claim 71, further comprising: means for preventing manualopening of the door.
 76. The access door assembly according to claim 71,wherein the journal is mounted proximal to a lower portion of the meansfor mounting.
 77. The access door assembly according to claim 71,wherein the door moves towards an operator when the door is urged to theopen position.